Cover: police at the Zizzi restaurant on Tuesday, near to where former Russian double agent Sergei Skripal was found. (Picture: PA)
Pub-goers and diners in Salisbury are being urged to wash clothing and possessions after traces of a nerve agent were found.
The warning came after investigators found traces of the chemical weapon at the Zizzi restaurant in the city centre.
Public Health England issued the advice as a precaution, but said the risk to the general public remains "low".
Anyone who was in The Mill pub between 1.30pm last Sunday and 11.10pm on Monday, or the nearby Zizzi restaurant between 1.30pm on Sunday and 9pm on Monday, are urged to follow the advice.
The eatery was hidden from view behind hoardings on Saturday as officers returned to search for evidence, with the BBC later reporting the nerve agent was detected in one part of the premises.
No-one else who was at the restaurant at the time is thought to be at risk, nor has it been suggested that their fellow diners had anything to do with the suspected attack, the BBC said.
Detective Sergeant Nick Bailey, who fell seriously ill after tending to the pair, released a statement from hospital saying "he does not consider himself a hero" and was "merely doing his job".
Cordons remain in place at a host of locations across the city, including Mr Skripal's house and the cemetery where his wife and son are buried.
During a joint press conference with emergency services colleagues, Temporary Chief Constable Kier Pritchard of Wiltshire Police said he was "unable to clarify how long" those crime scenes will be in place.
Currently, cordons are present at a number of sites around Salisbury, including around Mr Skripal's home and where he was found.
Scotland Yard said no exhumations had taken place.
Speaking following a meeting of the Government's Cobra emergencies committee, Ms Rudd said it was still too early to say who was responsible for the attack:
"This investigation is focused on making sure that we keep people safe and also that we collect all the evidence so that when it comes to attribution we will be absolutely clear where it should be.
"The police have said that if anybody thinks they have any additional information they would welcome them coming forward.
"There is also substantial amounts of CCTV they have to go through. This is a painstaking, detailed investigation and the police need to be given the space and time to get on with it."
Mr Skripal and his daughter Yulia are still fighting for their lives after being exposed to a toxic substance in the Wiltshire city.
Labour former cabinet minister Jack Straw has warned against a rush to judgment over Russian involvement in the Salisbury nerve agent attack.
Mr Straw drew comparison with the 2003 Iraq War when he was foreign secretary in Tony Blair's government.
"The evidence against Saddam Hussein having - and continuing to have - chemical and biological weapons was overwhelming, without any question," he told BBC1's Sunday Politics programme.
"That was the evidence Tony Blair and I used 15 years ago to persuade people to go to war against Iraq but it turned out to be completely incorrect. I have got the scars, literally, on my back in respect of this.
"You have got to be very, very careful in the heat of the moment, with people in the House of Commons and the newspapers screeching 'Something has got to be done' - always being inexplicit about what - in assuming that probabilities mean certainties."
Police said 21 people had been seen for medical treatment since the incident.
The figure includes members of the public and emergency staff, some of whom have had blood tests as well as receiving support and advice.
The attack is being treated as attempted murder.